Oil galleries are formed in an engine body, such as a cylinder block of an internal combustion engine, in order to supply oil to parts requiring oil supply, such as a hydraulic driving apparatus, in addition to bearing parts and sliding parts requiring lubrication (see Patent Publication 1). Such oil galleries are monolithically formed by casting-out at the time of casting of the cylinder block or by machining such as drilling. In addition, end opening portions, which are not used, opening at front and back wall surfaces of the cylinder block are closed by plugs.